Space-Confined Synthesis of Core-Shell BaTiO3@Carbon Microspheres as a High-Performance Binary Dielectric System for Microwave Absorption.

Binary dielectric composites are viewed as a kind of promising candidate for conventional magnetic materials in the field of microwave absorption. Herein, we demonstrate the successful fabrication of core-shell BaTiO3@carbon microspheres through a space-confined strategy. The electromagnetic properties of BaTiO3@carbon microspheres can be easily tailored by manipulating the relative content of carbon shells. It is confirmed that dielectric loss of these composites mainly benefits from conductivity loss, dipole orientation polarization, and interfacial polarization, and the core-shell configuration shows its positive contribution to the reinforcement of interfacial polarization. When the content of carbon shells is optimized, the as-obtained composite will display excellent microwave-absorption performance due to decent attenuation and well-matched impedance. The strongest reflection loss can reach up to -88.5 dB at 6.9 GHz with the absorber thickness of 3.0 mm, and the qualified bandwidth below -10.0 dB covers 9.0-12.0 GHz, when the thickness is designated at 2.0 mm. Such a performance in the X band is superior to those of most typical binary dielectric systems. More importantly, these BaTiO3@carbon microspheres maintain good performance after being treated under high-temperature and acidic conditions for a long time, manifesting their promising prospect for practical application. It is believed that these results may be helpful for the development of multicomponent dielectric systems as high-performance microwave absorbing materials.